Scenario

Oracle Client tries to connect Oracle Database Server.

Reason

The Oracle Advanced Encryption Option (ANO) is enabled as well as Protocol Adapter Encryption (typically when Client connects to TCPS port of Oracle Listener). Thats why "Double Encryption".

Solution

Disable ANO or Protocol Adapter Encryption.

How to disable ANO?

The solution lies in actual configuration of SQLNET.ORA configuration file.

You can turn off ANO for example:

In Case

Server->SQLNET.ORA-> ENCRYPTION_SERVER = REQUESTED | ACCEPTED

Set Parameter

Client->SQLNET.ORA-> ENCRYPTION_CLIENT = REJECTED

Note

After change is good practice, not must requirement, to restart Listener.

For Explanation or more Configuration Cases please follow:

Oracle Advanced Security Administrator's Guide